// Copyright (c) 2019 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.

#include <cstdint>
#include <cstdlib>
#include <iostream>
#include <memory>
#include <string>
#include <vector>

#include "gtest/gtest.h"
#include "leveldb/db.h"
#include "leveldb/write_batch.h"
#include "util/testutil.h"

namespace leveldb
{

    namespace
    {

        // Creates a random number in the range of [0, max).
        int GenerateRandomNumber(int max) { return std::rand() % max; }

        std::string CreateRandomString(int32_t index)
        {
            static const size_t len = 1024;
            char bytes[len];
            size_t i = 0;
            while (i < 8)
            {
                bytes[i] = 'a' + ((index >> (4 * i)) & 0xf);
                ++i;
            }
            while (i < sizeof(bytes))
            {
                bytes[i] = 'a' + GenerateRandomNumber(26);
                ++i;
            }
            return std::string(bytes, sizeof(bytes));
        }

    } // namespace

    TEST(Issue320, Test)
    {
        std::srand(0);

        bool delete_before_put = false;
        bool keep_snapshots = true;

        std::vector<std::unique_ptr<std::pair<std::string, std::string>>> test_map(
            10000);
        std::vector<Snapshot const *> snapshots(100, nullptr);

        DB *db;
        Options options;
        options.create_if_missing = true;

        std::string dbpath = testing::TempDir() + "leveldb_issue320_test";
        ASSERT_LEVELDB_OK(DB::Open(options, dbpath, &db));

        uint32_t target_size = 10000;
        uint32_t num_items = 0;
        uint32_t count = 0;
        std::string key;
        std::string value, old_value;

        WriteOptions writeOptions;
        ReadOptions readOptions;
        while (count < 200000)
        {
            if ((++count % 1000) == 0)
            {
                std::cout << "count: " << count << std::endl;
            }

            int index = GenerateRandomNumber(test_map.size());
            WriteBatch batch;

            if (test_map[index] == nullptr)
            {
                num_items++;
                test_map[index].reset(new std::pair<std::string, std::string>(
                    CreateRandomString(index), CreateRandomString(index)));
                batch.Put(test_map[index]->first, test_map[index]->second);
            }
            else
            {
                ASSERT_LEVELDB_OK(
                    db->Get(readOptions, test_map[index]->first, &old_value));
                if (old_value != test_map[index]->second)
                {
                    std::cout << "ERROR incorrect value returned by Get" << std::endl;
                    std::cout << "  count=" << count << std::endl;
                    std::cout << "  old value=" << old_value << std::endl;
                    std::cout << "  test_map[index]->second=" << test_map[index]->second
                              << std::endl;
                    std::cout << "  test_map[index]->first=" << test_map[index]->first
                              << std::endl;
                    std::cout << "  index=" << index << std::endl;
                    ASSERT_EQ(old_value, test_map[index]->second);
                }

                if (num_items >= target_size && GenerateRandomNumber(100) > 30)
                {
                    batch.Delete(test_map[index]->first);
                    test_map[index] = nullptr;
                    --num_items;
                }
                else
                {
                    test_map[index]->second = CreateRandomString(index);
                    if (delete_before_put)
                        batch.Delete(test_map[index]->first);
                    batch.Put(test_map[index]->first, test_map[index]->second);
                }
            }

            ASSERT_LEVELDB_OK(db->Write(writeOptions, &batch));

            if (keep_snapshots && GenerateRandomNumber(10) == 0)
            {
                int i = GenerateRandomNumber(snapshots.size());
                if (snapshots[i] != nullptr)
                {
                    db->ReleaseSnapshot(snapshots[i]);
                }
                snapshots[i] = db->GetSnapshot();
            }
        }

        for (Snapshot const *snapshot : snapshots)
        {
            if (snapshot)
            {
                db->ReleaseSnapshot(snapshot);
            }
        }

        delete db;
        DestroyDB(dbpath, options);
    }

} // namespace leveldb

int main(int argc, char **argv)
{
    testing::InitGoogleTest(&argc, argv);
    return RUN_ALL_TESTS();
}
